This invention relates to a vibration isolator used in a semiconductor manufacturing apparatus and/or an electron microscope, etc. More particularly, the invention relates to a vibration isolator, referred to as an active vibration isolator, for driving an actuator in accordance with a detection signal from a vibration sensor. The invention further relates to a device manufacturing apparatus such as an exposure apparatus having the above-mentioned vibration isolator, a device manufacturing method, a semiconductor manufacturing plant and a method of maintaining the device manufacturing apparatus.
In precision instruments such as electron microscopes and semiconductor device manufacturing apparatus, the transfer of vibration from the external environment to the apparatus proper must be minimized.
It is essential, therefore, that the precision equipment be mounted on a precision vibration isolator. In particular, since an XY stage for exposure in an exposure apparatus moves continuously and at high speed, it is required that the vibration isolator achieve, in good balance, a vibration isolating capability with regard to external vibration and a vibration damping capability with regard to internal vibration produced by operation of the mounted equipment itself.
An active-type vibration isolator has been put into practical use in recent years to meet these requirements. Such a vibration isolator makes it possible to control vibration effectively by driving an actuator in accordance with a detection signal from a vibration sensor. The active vibration isolator makes it possible to achieve balanced vibration isolating and vibration damping capabilities. This is difficult to realize with a passive vibration isolator that relies solely upon a support mechanism having spring and damper characteristics.
A typical embodiment of a vibration isolator seen in the prior art is disclosed in the specification of Japanese Patent Application Laid-Open No. 10-156144, entitled xe2x80x9cVibration Isolatorxe2x80x9d. In accordance with this disclosure, acceleration sensors are adopted as vibration sensors for sensing the vibration of a vibration isolation platform, and air springs are adopted as actuators for driving the vibration isolation platform. The acceleration sensors are arranged with their axes of detection pointing in the horizontal and vertical directions and detect acceleration of the vibration isolation platform in the horizontal and vertical directions.
The air springs, which support the vibration isolation platform in such a manner that their thrust producing axes agree with the horizontal and vertical directions, apply horizontal and vertical thrust to the vibration isolation platform. Vibration of the vibration isolation platform is suppressed in excellent fashion by applying so-called vibration feedback in accordance with which the air springs drive the vibration isolation platform along the horizontal and vertical directions in accordance with compensation values obtained by applying appropriate compensation to the detection signals from the acceleration sensors.
In a precision vibration isolator of this kind, it is common knowledge to use servo-type acceleration sensors, which exhibit excellent resolution with respect to minute vibration, for the purpose of sensing vibration of the vibration isolation platform. The principle of acceleration detection by a servo-type acceleration sensor will be described with reference FIG. 6A.
FIG. 6A illustrates an arrangement where a servo-type acceleration sensor is disposed in the horizontal direction. A case is fixed to a mounting surface and a pendulum is suspended from the case. Acceleration produced at the mounting surface is equal to an inertial force that acts upon the pendulum. In this servo-type acceleration sensor, a servo mechanism is provided in such a manner that the displacement of the pendulum is maintained at zero. The velocity of the mounting surface is sensed using a servo electromagnetic force.
The servo-type acceleration sensor also senses inclination of the mounting surface using the earth""s gravitational force, as shown in FIG. 6B. Thus, while the servo-type acceleration sensor is advantageous in that it can sense even DC components of acceleration, it is disadvantageous in terms of controlling vibration precisely.
More specifically, in a case where the servo-type acceleration sensor is disposed on a horizontal plane in order to sense acceleration in the horizontal direction and the horizontal direction is the direction of interest, a problem which arises is that inclination of the mounting surface, which is regarded as another component, also is sensed. The fact that another component is included in the detection signal is equivalent to application of measurement noise to the vibration-control feedback loop. This is a factor that impedes an improvement in the performance of the vibration isolator. If horizontal vibration feedback in the horizontal direction is applied in an active vibration isolator, vibration feedback cannot be applied properly because the detection signal includes another component that represents inclination. As a consequence, the vibration isolation platform is caused to vibrate instead of having its vibration suppressed.
A servo-type velocity sensor of the kind disclosed in the specification of Japanese Utility Model Publication No. 6-28698 (entitled xe2x80x9cServo-type Vibration Receiverxe2x80x9d) also has been put into practical use in recent years. Since velocity is obtained by an integration of acceleration, a velocity sensor is advantageous in that it has a low-frequency sensitivity that is higher than that of an acceleration sensor. Velocity sensors are utilized in architectural structures and in the measurement of ground vibration where observation of low-frequency components is important.
However, the principle of velocity detection by a servo-type velocity sensor is similar to the principle of acceleration detection by a servo-type acceleration sensor that uses a pendulum of the kind shown in FIGS. 6A and 6B. When velocity in the horizontal direction is sensed by a servo-type vibration sensor, the aforementioned problem still arises, namely, the fact that other components ascribable to inclination also are sensed.
Exactly the same problem arises also when a servo-type acceleration sensor or servo-type velocity sensor is disposed in the vertical direction. The sensor will sense not only vertical translational vibration but also inclination of the sensor mounting surface with respect to the vertical axis. As a consequence, when vibration feedback in the vertical direction is applied in an active-type vibration isolator, vibration feedback cannot be applied properly because the sensor signal includes inclination-related components. As a consequence, the vibration isolation platform is caused to vibrate instead of having its isolation suppressed.
In other words, because a sensor-type vibration isolator whose use in a precision vibration isolator is common knowledge is influenced by inclination of the vibration isolation platform, the performance of the vibration isolator is degraded when vibration feedback is applied.
Accordingly, an object of the present invention is to provide a vibration isolator for sensing vibration only in a horizontal translational direction or vertical translational direction without being affected by inclination of a vibration isolation platform, thereby making it possible to control vibration in an ideal fashion, as well as a device manufacturing apparatus and method, a semiconductor manufacturing plant and a method of maintaining the device manufacturing apparatus that employ the vibration isolator.
According to the present invention, the foregoing object is attained by providing a vibration isolator comprising: a vibration isolation platform, a vibration sensor installed on the vibration isolation platform, and an angle sensor for sensing an inclination angle of the vibration isolation platform, wherein a detection signal from the vibration sensor is corrected based upon an output from the angle sensor, and the corrected detection signal is used in order to suppress vibration of the vibration isolation platform.
The detection signal from the vibration sensor contains an inclination component owing to the influence of inclination of the vibration isolation platform. The inclination component contained in the output of the vibration sensor, however, is cancelled out using the angle sensor. As a result, it is possible to sense the vibration component more precisely than heretofore and, hence, vibration control of the vibration isolator can be performed in an ideal fashion.
The angle sensor should be one that can sense the inclination component sensed by the vibration sensor. Though a gyroscope can be mentioned as one example, use of a displacement sensor is particularly preferred. Preferably, two or more of such displacement sensors are installed in order to sense vertical displacement of the vibration isolation platform at two or more locations. Each displacement sensor senses vertical displacement of the vibration isolation platform at its particular position, and the angle of inclination of the vibration isolation platform can be calculated from the difference between the detection signals produced by the displacement sensors.
Inclination of the vibration sensor is compensated for by causing an appropriate inclination compensator to act upon the angle of inclination and then subtracting the compensated value from the detection signal of the vibration sensor. This makes it possible to sense translational vibration of the vibration isolation platform accurately without the influence of platform inclination. The inclination compensator converts the inclination signal, which is output from the angle sensor, to an inclination correction signal that is equivalent to the inclination component of the vibration isolation platform sensed by the vibration sensor, thereby making it possible to cancel out the inclination component of the vibration isolation platform, which is sensed by the vibration sensor, by the inclination correction signal.
An applicable vibration sensor in the present invention is one that can sense vibration of the vibration isolation platform. In particular, it is preferred that the vibration sensor be of the type in which the detection signal includes a vibration component and an inclination component. More specifically, the sensor may be a velocity sensor or an acceleration sensor. Generally, in a precision vibration isolator, a servo-type velocity sensor is used as the velocity sensor and a servo-type acceleration sensor is used as the acceleration sensor.
As for the overall structure of the vibration isolator according to the present invention, the vibration isolation platform is supported along two axes, namely, the vertical and horizontal axes, by three or more actuators, and the detection signal from the vibration sensor is fed back to drive the actuators, thereby suppressing translational vibration of the vibration isolation platform along two axes, namely, the vertical and horizontal directions, and rotational vibration of the vibration isolation platform about two axes, namely, the vertical and horizontal directions. The correction of the detection signal from the vibration sensor needs to be carried out only when vibration of the vibration isolation platform in the horizontal or vertical translational direction is fed back.
An apparatus for manufacturing a semiconductor device according to the present invention is provided for executing various processes when a semiconductor device is manufactured through these processes. The apparatus comprises the vibration isolator of the present invention and a main body of the apparatus, and the main body of the apparatus is installed on a vibration isolation platform. Examples of the manufacturing apparatus that can be mentioned are an exposure apparatus, a resist treatment apparatus, an etching apparatus, a heat treatment apparatus, a thin-film forming apparatus, a smoothing apparatus, an assembly apparatus and an inspection apparatus.
The manufacturing apparatus further includes a display, a network interface and a computer for executing network software, and it is possible for maintenance information for the manufacturing apparatus to be communicated by data communication. The network software preferably provides the display with a user interface for accessing a maintenance database, which is connected to an external network of a plant at which the manufacturing apparatus has been installed, and which is supplied by a vendor or user of the manufacturing apparatus, thereby making it possible to obtain information from the database via the external network.
A method of manufacturing a semiconductor device according to the present invention comprises the steps of placing a group of manufacturing apparatus for performing various processes, inclusive of the manufacturing apparatus of the present invention, in a plant for manufacturing semiconductor devices, and manufacturing a semiconductor device by performing a plurality of processes using this group of manufacturing apparatus. The method may further include steps of interconnecting the group of manufacturing apparatus by a local-area network, and communicating, by data communication, information relating to at least one manufacturing apparatus in the group of manufacturing apparatus between the local-area network and an external network outside the plant.
Further, maintenance information for the manufacturing apparatus may be obtained by accessing, by data communication via the external network, a database supplied by a vendor or user of the manufacturing apparatus, or production management may be performed by data communication with a semiconductor manufacturing plant other than the first-mentioned semiconductor manufacturing plant via the external network.
A semiconductor manufacturing plant according to the present invention comprises: a group of manufacturing apparatus for performing various processes, inclusive of the manufacturing apparatus of the present invention, a local-area network for interconnecting the group of manufacturing apparatus, and a gateway for making it possible to access, from the local-area network, an external network outside the plant, whereby information relating to at least one of the manufacturing apparatus can be communicated by data communication.
A method of maintaining the device manufacturing apparatus according to the present invention installed in a semiconductor manufacturing plant comprises the steps of: providing a maintenance database, which is connected to an external network of the semiconductor manufacturing plant, by a vendor or user of the manufacturing apparatus, allowing access to the maintenance database from within the semiconductor manufacturing plant via the external network, and transmitting maintenance information, which is stored in the maintenance database, to the side of the semiconductor manufacturing plant via the external network.
Other features and advantages of the present invention will be apparent from the following description taken in conjunction with the accompanying drawings, in which like reference characters designate the same or similar parts throughout the figures thereof.